Epoxy compositions are widely used in many applications including, among others, the electronics industry. In some applications they are blended with rubber to provide enhanced flexibility, toughness, and adhesive strength. One such application is as a flexible cover layer for flexible printed wiring boards.
While epoxies offer many desirable properties, they are known to be undesirably flammable, often requiring the addition of a flame retardant to a curable epoxy formulation in order to meet fire resistance standards. In addition, it is desirable to have a curable epoxy composition with as long a shelf life as possible. One approach to achieving long shelf-life is to prepare a so-called latent curing catalyst or cross-linking agent (curing agent). A latent catalyst or curing agent could be inactive at room temperature but thermally activated at a temperature well above room temperature. For practical reasons, it is desirable for uncured compositions to remain stable at temperatures up to 40 or 50° C. Thus a latent catalyst or curing agent activated at a temperature above 50° C. but below a temperature that will degrade the epoxy or electronic circuit elements is highly desirable in the art. A catalyst or curing agent that further obviates the need for a flame retardant additive would be so much the better for the properties of the resultant composition.